Patch Test Results of 210 Cosmetics in Shanghai, China

MethodsPatch tests. Participants arrived at the laboratory and were informed of the trial procedures and objectives. In this study, qualified patch test chambers with an area not exceeding 50 mm² and a depth of approximately 1 mm were used. The test substance was placed into the chamber of the patch test device, with a dosage of approximately 0.020 g to 0.025 g (for solids or semi-solids) or 0.020 mL to 0.025 mL (for liquids). When the test substance was the original product, the control chamber was left blank (with no substance placed); when the test substance was a diluted product, the control chamber contained the diluent of the product. The patch test chamber with the test substance was then applied to the participant's back or the flexor side of the forearm using hypoallergenic tape, and gently pressed with the palm to ensure even adhesion to the skin for a duration of one day. Skin reactions were observed at 30 minutes (after the pressure marks disappeared), 1 day, and 2 days following the removal of the patch test chamber. The patch test results were interpreted according to the Chinese regulation “Safety and Technical Standards for Cosmetics” (2015 edition) and the recommendations of the International Contact Dermatitis Research Group (ICDRG) 23,24. The scoring system for patch test is shown in Table 1, and the observations were recorded.The study was conducted from March 2023 to August 2024, with a total of 18 trials performed. Each trial involved 30 to 37 participants. Due to limitations of the test area, the number of cosmetics tested in each trial did not exceed 17. Participants. A total of 567 participants aged 18 to 60 years were involved in this study, comprising 35 males (6.17%) and 532 females (93.83%). All participants met the following criteria: 1) Voluntary participation; 2) No use of antihistamines within the past week or immunosuppressants within the past month; 3) No application of anti-inflammatory drugs on the test site within the past two months; 4) Non-insulin-dependent diabetic patients; 5) Not highly sensitive individuals; 6) No skin imperfections on the test site that could affect the interpretation of results; 7) No clinical treatment received within the past six months.All participants provided written informed consent. The study was approved by the Shanghai Jiyan Biomedical Ethics Committee (approval number: JYE20230203001) and was conducted in accordance with the principles of the Declaration of Helsinki. Cosmetics. The cosmetics selected for testing were chosen randomly, without any limitation on type. The tested cosmetics were categorized based on their application methods, dosage forms, and seasons. The criteria and information for classification are presented in Table 2. According to the definition in the Chinese regulation " Safety and Technical Standards for Cosmetics" (2015 edition), cosmetics were classified into two categories based on application methods: leave-on cosmetics and rinse-off cosmetics. Based on dosage forms, cosmetics were divided into liquids, gels, sprays, creams and masks. In this study, the terms 'liquids,' 'gels,' 'sprays,' 'creams,' and 'masks' are used to describe the dosage forms of the tested cosmetics, corresponding to liquid cosmetics, gel cosmetics, spray cosmetics, creams and lotions, and facial mask cosmetics, respectively. Cosmetics were also categorized by season according to the temperature and humidity in Shanghai, resulting in the classification of cosmetics for spring, summer, autumn, and winter. Data processing. The data from the 18 patch tests were compiled and summarized, covering a total of 210 cosmetics, which were labeled according to their different types. The patch test results of the cosmetics exhibited three types of skin reactions: negative reactions, doubtful reactions (only mild erythema), and weak positive reactions (erythema, infiltration, and possibly a few papules). In this study, doubtful reactions and weak positive reactions were collectively referred to as non-negative reactions. The non-negative reaction rate was calculated as the number of cosmetics showing skin reactions divided by the total number of cosmetics. The total number of reactions was the sum of doubtful reactions and weak positive reactions. The patch test results were compared among cosmetics with different application methods, dosage forms, and seasonal categories.